Fermentative production of the unnatural amino acid l-2-aminobutyric acid based on metabolic engineering

Abstract

Background l -2-aminobutyric acid ( l -ABA) is an unnatural amino acid that is a key intermediate for the synthesis of several important pharmaceuticals. To make the biosynthesis of l -ABA environmental friendly and more suitable for the industrial-scale production. We expand the nature metabolic network of Escherichia coli using metabolic engineering approach for the production of l -ABA. Results In this study, Escherichia coli THR strain with a modified pathway for threonine-hyperproduction was engineered via deletion of the rhtA gene from the chromosome. To redirect carbon flux from 2-ketobutyrate (2-KB) to l -ABA, the ilvIH gene was deleted to block the l -isoleucine pathway. Furthermore, the ilvA gene from Escherichia coli W3110 and the leuDH gene from Thermoactinomyces intermedius were amplified and co-overexpressed. The promoter was altered to regulate the expression strength of ilvA* and leuDH . The final engineered strain E. coli THR Δ rhtA Δ ilvIH /Gap- ilvA *-Pbs- leuDH was able to produce 9.33 g/L of l -ABA with a yield of 0.19 g/L/h by fed-batch fermentation in a 5 L bioreactor. Conclusions This novel metabolically tailored strain offers a promising approach to fulfill industrial requirements for production of l -ABA. Electronic supplementary material The online version of this article (10.1186/s12934-019-1095-z) contains supplementary material, which is available to authorized users.

Targeting metabolic driving and minimization of by‐products synthesis for high‐yield production of D‐pantothenate in Escherichia coli

“…[17,22] Therefore, the destruction of amino acid branches is often used as a common strategy for the construction of microbial cell factories. [23][24][25] However, it is time-consuming and com-plicated to eliminate the competition from a variety of amino acids by gene-editing, and the resulting auxotrophic strains would increase the difficulty and cost in the fed-batch fermentation. Thus, it is important to find a simple and effective strategy to improve this traditional and complicated way.…”

Metabolic Detoxification of 2-Oxobutyrate by Remodeling Escherichia coli Acetate Bypass

“…However, accumulation of 2-OBA in most microorganisms leads to severe cellular toxicity, including growth arrest or even death [ 8 ]. In the biosynthesis process of 2-OBA derivatives, such as l -isoleucine [ 9 , 10 ], l -2-aminobutyric acid [ 11 ], 1-propanol [ 12 ] and 1-butanol [ 13 , 14 ], the expression level of threonine deaminase catalyzing the breakdown of l -threonine to generate 2-OBA tends to be limited to avoid the toxic accumulation of 2-OBA, which imposes a restriction on the improvement of its downstream flux and target product productivity. This type of biological toxicity not only retards the growth of the fermentation strains, but also blocks the biosynthesis of target products.…”

Active-site engineering of ω-transaminase from Ochrobactrum anthropi for preparation of L-2-aminobutyric acid

“…L-ABA is an essential chiral building block for various pharmaceutical drugs, such as the antiepileptic drug levetiracetam and the antituberculosis drug ethambutol, etc. [ 1 – 3 ]. The Asymmetric synthesis of L-ABA with both chemocatalytic and biocatalytic strategies has been developed and the biocatalytic methods have attracted growing attention due to environmental and social demands for green processes in the chemical industry recently [ 4 ].…”